Information about the topology or conformation of a bioentity can be very useful as a diagnostic or research tool. For example, mis-folded conformational states of a bioentity can be a determinant of a disease state (e.g. prions). Conformational assays have been performed on either a single molecule or between two or more interacting molecules. Intrinsic conformational flexibility of bioentities is well documented in the literature and has been used in the prior art as a screening tool for drug discovery. Other indirect bind screening tools exist such as displacement assays coupled with mass spectroscopy as well as capillary electrophoresis are known.
Biosensors that measure changes in refractive index provide an attractive option for detecting conformational changes in bioentities, particularly changes in conformation induced by a ligand that has an affinity for the bioentity. However, in some cases the molecular weight of the ligand of interest may not be sufficient to provide a direct bind response (e.g. binders below 250 Dalton). Therefore, indirect methods that enable detection of low molecular weight ligand binders on refractive index detecting systems would be of great value. In addition, stereo-specific conformational changes between the two interacting molecules or within a single molecule may be critical in understanding the mechanism of action of the bioentity or ligand that has an affinity for the bioentity.
Described herein are methods for detecting conformational changes in bioentities. The methods involve the use of evanescent detection as a way for detecting conformational changes in a bioentity or changes that occur when the bioentity interacts with another molecule that induces a conformational change in the bioentity. The methods can be use by themselves or in combination with other with other detection platforms. The methods described herein can be a useful tool in research and provide valuable structural information of bioentities that current detection methods cannot easily provide.